Bump testtools from 2.7.2 to 2.8.0 in /constraints

Bumps [testtools](https://github.com/testing-cabal/testtools) from 2.7.2 to 2.8.0.
- [Release notes](https://github.com/testing-cabal/testtools/releases)
- [Changelog](https://github.com/testing-cabal/testtools/blob/master/NEWS)
- [Commits](testing-cabal/testtools@2.7.2...2.8.0)

---
updated-dependencies:
- dependency-name: testtools
  dependency-version: 2.8.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

constraints/constraints-py38.txt

@@ -115,7 +115,7 @@ sortedcontainers==2.4.0
 soupsieve==2.7
 streamdeck==0.9.6
 sympy==1.13.3
-testtools==2.7.2
+testtools==2.8.0
 threadpoolctl==3.5.0
 tifffile==2023.7.10
 triangle==20250106

constraints/constraints-py39.txt

@@ -114,7 +114,7 @@ sortedcontainers==2.4.0
 soupsieve==2.8
 streamdeck==0.9.8
 sympy==1.14.0
-testtools==2.7.2
+testtools==2.8.0
 threadpoolctl==3.6.0
 tifffile==2024.8.30
 triangle==20250106